I have a 1995 YJ 2.5l thats my DD and it has over the course of last Friday to Sunday, gone from burning absolutely no oil to using a quart every 3 days. It has done 10+ 1200 km continuous drives this summer and has had no engine problems otherwise. The only recent change has been the 4.0l throttle body but I installed that about a month ago so I would imagine problems with it wouldn't just be starting now. The jeeps exhaust does have a noticeable oil smell when on the throttle, but does NOT smoke at all whatsoever. There is also no oil on my parking spot at home or at work and no leaks visible underneath.

Attempts to fix the problem this week involved changing the oil to 40 weight from 20 (was told if my seals/rings are worn out I can eek a little more life out of it by running heavier oil), it made it burn at the same rate but now it stinks like oil when I park and it didn't before, and also I pulled out the "CCV" (i think) line and fitting on the valve cover thats under vaccuum to the manifold to clean it but it seems to pass air just fine as does the line that goes to the PCV valve look-alike, there is a little bit of oil on my filter but it seems to be coming from the line that pulls air into the block from the top of the valve cover. It has had a very small amount of oil around that orifice and on the air filter since I got it 2 years ago though so I'm left clueless as to what it could be.

I could be wrong, but if I understand correctly my jeep will smoke if the piston rings/seals are gone right? Another thing I heard was to check the plugs but I don't know what for. Also compression is still good.

It's good to hear the compression is good. This means the piston rings and valves are still good. I would suspect the valve stem seals though. On the plugs, you would be looking for oil fouling, usually a very thick black deposit.
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I have a 1995 YJ 2.5l thats my DD and it has over the course of last Friday to Sunday, gone from burning absolutely no oil to using a quart every 3 days. It has done 10+ 1200 km continuous drives this summer and has had no engine problems otherwise. The only recent change has been the 4.0l throttle body but I installed that about a month ago so I would imagine problems with it wouldn't just be starting now. The jeeps exhaust does have a noticeable oil smell when on the throttle, but does NOT smoke at all whatsoever. There is also no oil on my parking spot at home or at work and no leaks visible underneath.

Attempts to fix the problem this week involved changing the oil to 40 weight from 20 (was told if my seals/rings are worn out I can eek a little more life out of it by running heavier oil), it made it burn at the same rate but now it stinks like oil when I park and it didn't before, and also I pulled out the "CCV" (i think) line and fitting on the valve cover thats under vaccuum to the manifold to clean it but it seems to pass air just fine as does the line that goes to the PCV valve look-alike, there is a little bit of oil on my filter but it seems to be coming from the line that pulls air into the block from the top of the valve cover. It has had a very small amount of oil around that orifice and on the air filter since I got it 2 years ago though so I'm left clueless as to what it could be.

I could be wrong, but if I understand correctly my jeep will smoke if the piston rings/seals are gone right? Another thing I heard was to check the plugs but I don't know what for. Also compression is still good.

Any ideas are awesome.
Thanks

If you are using oil then there are three possibilities;
#1 Someone is stealing your oil.
#2 You are leaking oil out through a seal but you see nothing on the ground
#3 You are burning oil.
Since your exhaust is smelling oil then you are probably burning it. BUT that means the leak is internal. My guess would be valve guide/seal.

What has happened to your oil pressure??

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Senators and Congressman should wear uniforms like NASCAR drivers so we could identify their corporate sponsors....

My oil pressure has always been 3 mpa (middle at idle regardless of temp) through 5 mpa (towards the high end but not all the way there since I got it, changing to the 40 weight made it go to about 3.75 or so at idle and the same as before at higher rpms.

I am quite confident there is no oil leaking out of the actual block into the engine compartment, the engine is very clean, about 3 weeks ago I went ocd cleaning my jeep and doing repairs because it gets to -50 Celcius for weeks at a time here in the winter so I can't work on it during winter unless I rent a garage. The only visible leak of anything is the clutch slave cylinder but I have a new one on order, should be irrelevant to losing oil though. Also I looked at the coolant today, as green as ever, no oil.

Is there any "tricks" to determining if the oil is actually burning through the valve guides or any where else? When you say valve guides are you referring to the ones on top of the head that the physical valves slide up and down through? How hard are they to change? I work on small engines regularly, just not full size ones.

Also the reason I say the exhaust smells like oil is because one of my friends following me to a trail head told me he smells oil but I myself have not smelled anything in the exhaust which would lead me to believe its only at higher RPMs or under load that it occurs.

Is there any "tricks" to determining if the oil is actually burning through the valve guides or any where else? When you say valve guides are you referring to the ones on top of the head that the physical valves slide up and down through? How hard are they to change? I work on small engines regularly, just not full size ones.

Also the reason I say the exhaust smells like oil is because one of my friends following me to a trail head told me he smells oil but I myself have not smelled anything in the exhaust which would lead me to believe its only at higher RPMs or under load that it occurs.

I'm not aware of any tricks other than to look at the intake valves and see what is on the back side of them.

Yes, the valve guides on top of the head, where the physical valves move. It's not difficult to change the seals, because the concept is simple. The labor can be a PITA because there's 16 of them, and you have to remove the valve springs and keepers.

You do not need to remove the head or anything, just use some compressed air to hold the valves shut - they make special adapters that screw into the spark plug hole and hook up to your air compressor.

The seals are just little rubber cups which push on and pull off the valve stems, located inside of the valve springs. They're fairly cheap.

At high RPMs or under load is exactly the time when valve seals will leak in fact. Especially since you are dealing with rubber parts, which are very old, and run in a bath of hot oil for their whole lives.
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Last edited by oldtime_ironman; 10-17-2011 at 09:07 PM.
Reason: tricks